The story retells, with some poetic license, the lives of five Irish-American Sullivan brothers, who grew up in Iowa during the days of the Great Depression and served together in the United States Navy during World War II.

The Irish-American Catholic Sullivan brothers are introduced through a progression of baptisms: George Thomas in 1914, Francis "Frank" Henry in 1916, Joseph "Joe" Eugene in 1918, Madison "Matt" Abel in 1919, and Albert "Al" Leo in 1922 in their hometown of Waterloo, Iowa.

The brothers are shown getting into their fair share of trouble growing up: a fight, a near drowning (after which their mother makes them promise not to set foot on a boat again until they are adults), and accidentally flooding the kitchen.

On the day that George wins a motorcycle race, Al meets Katherine Mary (played by Anne Baxter) an only child who lives with her father.

The brothers insist that they serve on the same ship, but the recruiting officer, LCDR Robinson (played by Ward Bond), states that the Navy can make no such guarantees.

George survived before suffering from delirium as a result of hypernatremia, although some sources say he went mad with the grief of losing his brothers, and four or five days later he slipped quietly out of the raft, never to be seen again.